U.S. Pat. No. 3,552,120 - William T. Beale discloses a Stirling cycle thermal engine or refrigerating device wherein there is no primary mechanical connection between the displacer pistons and their associated power pistons. In my patent, the use of the displacer piston rod as a displacer movement initiating means is disclosed and claimed. This application is directed to alternate means for initiating motion in the displacer piston wherein means cooperating with the displacer piston rod and the power piston causes the displacer piston to move at a fixed point in the travel of the power piston, thus insuring rapid displacer piston motion at the proper portion of the engine's cycle resulting in more complete transfer of the gases between the hot and cold displacer cylinder spaces which in turn results in an increased cyclic work potential of the engine.
It has been found that any influence which results in improper displacer phasing can result in poor distribution of the hot and cold gases during expansion and compression giving rise to thermal hysteresis and lower thermal efficiency as discussed in SAE Paper 730647, June 18 - 22, 1973.